To elucidate the molecular composition of cell surfaces in the mammalian nervous system we shall use a combination of immunological, biochemical and immunocytological techniques. We propose to follow three lines of investigation of cell surface constituents on normal and malignant nervous system cells utilizing antisera to nervous system specific antigens (NS-1 to NS-5). Biochemical characterization will be carried out to probe for the molecular homogeneity of antigens, to purify them, identify their chemical nature and raise antibodies to the purified fractions. We will seek antigenic entities in supernatants of cell cultures and in detergent of salt extracts of plasma membranes obtained by subcellular fractionation after prelabelling the cell surface with radioisotopes. Antigens in soluble form will be immunoprecipitated with antibody, resolubilized and analyzed by polyacrylamide gel electrophoresis. Biochemical fractionation using Folch partitioning will allow for detection of phospho- and glycolipids. The cellular and subcellular localization of antigens in histological sections at the light and electron microsopic levels will be attempted by using various fixation procedures, highly purified immunological reagents and various visual markers (fluorescein, horseradish peroxidase and sheep red blood cells). We propose to isolate nervous system cell classes through immunoselection techniques with selective antisera. Preparative methods will utilize the principle of fluorescein-activated automatic cell sorting, the mixed adsorption hybrid antibody test with sheep red blood cells, and the cytotoxic elimination of antigen-positive cell types. The preparation of viable single cell suspensions from adult brain will be carried out by the "brainwash" procedure.